<?php
require_once __DIR__ . '/BasePosting.php';

/**
 * PurchasePosting
 *
 * Builds the GL journal entry for a Purchase Order (GRN).
 * Typical formula: DR Inventory (per SKU) + DR Input VAT / CR Accounts Payable.
 *
 * Amount keys:
 *   grand_total — full PO total (used for AP credit line)
 *   tax         — VAT portion
 *   total       — pre-tax (grand_total - tax), split per SKU via purchase_account_code
 *   amount      — alias of grand_total
 */
class PurchasePosting extends BasePosting
{
    protected function getDocType(): string { return 'purchase_order'; }

    protected function fetchDocument(int $id): array
    {
        $sth = $this->pdo->prepare(
            "SELECT p.*, COALESCE(c.contact_name, '') AS contact_name
             FROM td_purchase_order p
             LEFT JOIN md_contact c
               ON c.company_id = p.company_id AND c.id = p.contact_id
             WHERE p.company_id = :cid AND p.id = :id
             LIMIT 1"
        );
        $sth->execute([':cid' => $this->companyId, ':id' => $id]);
        $doc = $sth->fetch(PDO::FETCH_ASSOC);
        if (!$doc) throw new Exception("Purchase order #{$id} not found.");

        $sth2 = $this->pdo->prepare(
            "SELECT * FROM td_purchase_order_item
             WHERE company_id = :cid AND order_id = :id
             ORDER BY item_id ASC"
        );
        $sth2->execute([':cid' => $this->companyId, ':id' => $id]);
        $doc['items'] = $sth2->fetchAll(PDO::FETCH_ASSOC);

        return $doc;
    }

    protected function getAmounts(array $doc): array
    {
        $grand_total = abs((float)$doc['grand_total']);
        $tax         = abs((float)$doc['tax']);
        return [
            'grand_total' => $grand_total,
            'tax'         => $tax,
            'total'       => $grand_total - $tax,
            'amount'      => $grand_total,
        ];
    }

    protected function getDocDate(array $doc): string
    {
        return $doc['po_date'] ?? date('Y-m-d');
    }

    public function build(int $id, ?int $formula_id = null): array
    {
        $doc      = $this->fetchDocument($id);
        $formula  = $this->resolveFormula($this->getDocType(), $formula_id);
        $amounts  = $this->getAmounts($doc);
        $doc_date = $this->getDocDate($doc);
        $period   = substr($doc_date, 0, 7);
        $dept_id  = (int)($doc['department_id'] ?? 0);

        $lines = [];
        foreach ($formula['items'] as $item) {
            $amount = abs((float)($amounts[$item['amount_key']] ?? 0));
            if ($amount == 0) continue;

            if ($item['amount_key'] === 'total') {
                $split_lines = $this->buildSkuSplitLines($doc['items'], $item, $amount, $dept_id);
                if ($split_lines) {
                    $lines = array_merge($lines, $split_lines);
                    continue;
                }
            }

            $lines[] = [
                'account_code'  => $item['account_code'],
                'department_id' => $dept_id,
                'debit'         => $item['drcr'] === 'D' ? $amount : 0.0,
                'credit'        => $item['drcr'] === 'C' ? $amount : 0.0,
                'description'   => (string)($item['description'] ?? ''),
            ];
        }

        return [
            'formula_id' => (int)$formula['id'],
            'period'     => $period,
            'doc_date'   => $doc_date,
            'lines'      => $lines,
        ];
    }

    private function buildSkuSplitLines(array $items, array $formula_item, float $amount, int $dept_id): array
    {
        $items = array_values(array_filter($items, function($row) {
            return abs((float)($row['total_price'] ?? 0)) > 0.0000001;
        }));

        if (!$items) return [];

        $skus = array_values(array_unique(array_filter(array_column($items, 'product_sku'))));
        $account_map = [];
        if ($skus) {
            $placeholders = implode(',', array_fill(0, count($skus), '?'));
            $sth = $this->pdo->prepare(
                "SELECT sku, purchase_account_code FROM md_product
                 WHERE company_id = ? AND sku IN ({$placeholders})"
            );
            $sth->execute(array_merge([$this->companyId], $skus));
            foreach ($sth->fetchAll(PDO::FETCH_ASSOC) as $row) {
                $account_map[$row['sku']] = trim((string)($row['purchase_account_code'] ?? ''));
            }
        }

        $base_total = array_reduce($items, function($carry, $row) {
            return $carry + abs((float)($row['total_price'] ?? 0));
        }, 0.0);
        if ($base_total <= 0) return [];

        $remaining = round($amount, 4);
        $last = count($items) - 1;
        $lines = [];

        foreach ($items as $idx => $row) {
            $line_amount = $idx === $last
                ? $remaining
                : round($amount * (abs((float)$row['total_price']) / $base_total), 4);
            $remaining = round($remaining - $line_amount, 4);
            if (abs($line_amount) <= 0.0000001) continue;

            $sku = trim((string)($row['product_sku'] ?? ''));
            $account_code = ($sku !== '' && ($account_map[$sku] ?? '') !== '')
                ? $account_map[$sku]
                : (string)$formula_item['account_code'];

            $name = trim((string)($row['product_name'] ?? ''));
            $desc = trim((string)($formula_item['description'] ?? ''));
            $item_desc = trim($sku . ($name !== '' ? ' - ' . $name : ''));
            if ($item_desc !== '') {
                $desc = $desc !== '' ? $desc . ': ' . $item_desc : $item_desc;
            }

            $lines[] = [
                'account_code'  => $account_code,
                'department_id' => $dept_id,
                'debit'         => $formula_item['drcr'] === 'D' ? $line_amount : 0.0,
                'credit'        => $formula_item['drcr'] === 'C' ? $line_amount : 0.0,
                'description'   => $desc,
            ];
        }

        return $lines;
    }
}